Hydrogen gas has a number of important industrial applications including in petroleum refining, powering fuel cells, in production and processing of chemicals, and in semi-conductor materials manufacture. The earth's supply of hydrogen does not exist as large deposits of hydrogen gas, but is carried on other widely available molecules such as water or as hydrocarbons from petroleum oil or coal. As a result, hydrogen gas for use in the industrial application mentioned above is usually produced from water and hydrocarbon starting materials with a series of catalytic steps which generally provide hydrogen gas along with by products including oxygen, carbon monoxide and carbon dioxide.
In one important industrial process for the production of hydrogen, a hydrocarbon such as methanol, natural gas, gasoline, or diesel fuel is converted in a series of steps into a hydrogen rich gas. In an initial reaction such as steam reforming or partial oxidation, a hydrocarbon is reacted with water or oxygen to form hydrogen gas along with other by-products consisting mainly of carbon monoxide and carbon dioxide. The carbon monoxide produced in the initial reaction may be further reacted with water to yield additional amounts of hydrogen. The water gas shift reaction is the name given to the reaction of carbon monoxide, produced for example in the reforming process, with water to form hydrogen and carbon dioxide. Thus, the water gas shift reaction is a key reaction in the conversion of hydrocarbons into a hydrogen rich gas. Not only does the water gas shift reaction function to increase the yield of hydrogen from the process, it also may be valuable for removing undesired carbon monoxide from the reaction stream.
The water gas shift reaction, as are other reactions in the production of hydrogen from hydrocarbons, is generally carried out by passing a gas stream containing reactants over a solid catalyst in a heterogeneous reaction. The rate of conversion of the reactant into hydrogen and the overall yield of hydrogen is dependent on the function and the nature of the catalyst used. In addition, the size, weight, and cost of systems used to generate hydrogen depend on the efficiency of the catalyst for the water gas shift reaction and for other reactions in the overall process. Efficient catalysts for the water gas shift reaction would therefore be desirable because by using such catalysts the sizes of the systems used to produce hydrogen gas can be decreased and/or the rate of hydrogen production from such systems could be increased.